Sobriety testing, which includes testing for both alcohol and illegal drugs, has taken a prominent role in ensuring a safe and efficient society. For example, ignition interlocks on vehicles have proven their worth in preventing intoxicated drivers from entering the roadways and causing serious, including fatal, accidents. Sobriety testing has also allowed authorities, such as courts and law enforcement agencies, to monitor compliance with the court-ordered restrictions imposed on persons having committed an alcohol or drug related offense. Among other things, with the availability of reliable sobriety testing systems, such offenders can continue travel to work, school, or rehabilitation and thus contribute to society, rather than be a burden.
Attempts to circumvent these sobriety testing systems is significant problem. For example, an intoxicated driver might try to circumvent a breathalyzer-based vehicle sobriety interlock system by introducing air from an air compressor, compressed air canister, balloon, or other source of intoxicant-free air. And while a number of anti-circumvention techniques suitable for use in sobriety testing systems are known in the art, these techniques are subject to a number of significant limitations. For example, some known anti-circumvention techniques used with breathalyzer-based systems require that the person being tested manipulate the breath air flow into the test apparatus. In the blow-hum technique, the user starts with a normal blow of air, then switches to a blow of air combined with a hum. In the blow-suck technique, the user starts with a normal blow then quickly reverses to a suck or inhale. In the blow-blow technique, the user starts with a normal blow then changes to a harder blow or softer blow.
These air manipulation techniques are subject to some serious disadvantages. Among other things, they are difficult for the human test subject to master and require consistency and patience for even sober users to pass each time. Moreover, the blow-suck technique can be unhygienic.